We've used Hale pet doors in three different houses here in SE Alaska. They're double flapped and seal pretty well against our long winter storms. They're not cheap, but we've been happy with them.

We bought 8 Endura kennel pet doors about 4 months ago - so far so good - a young dog chewed up a flap in his run and we can replace the flap. They seem to work very well - magnetic etc. They are very quit. We got the simpler "kennel" design and use an guillotine on the inside we got From Gun Dog Supply.

We bought a Plexidor pet door and love it. The doors are solid clear plastic and very thick. We have had two of them. The first was the super giant size that can fit a St Bernard. We didn't have a dog that size, but we had a beagle (short legs) and a long legged shepherd mix. To have a door that went low enough for the beagle and was high enough for the shepherd mix, this was the best solution.

That dog door was moved into 2 other doors, and worked great for many years. Then both those dogs passed away and we got a smaller dog, who is only 35 pounds. So we bought another plexi-door that was his size (no need to have a huge door for a smallish dog).

We still have the original door, and if a big dog walks into our life we will install it into yet another door :)

You can get replacement insulating strips for the Plexidor on their website. I won't lie, these doors are NOT cheap but they are a once in a lifetime purchase ... Unless you change the size of dogs you have :)

Here is a link that might be useful: Plexidor website